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-rw-r--r--src/resolve/resolved-etc-hosts.c467
1 files changed, 467 insertions, 0 deletions
diff --git a/src/resolve/resolved-etc-hosts.c b/src/resolve/resolved-etc-hosts.c
new file mode 100644
index 0000000..8a58db4
--- /dev/null
+++ b/src/resolve/resolved-etc-hosts.c
@@ -0,0 +1,467 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include "fd-util.h"
+#include "fileio.h"
+#include "hostname-util.h"
+#include "resolved-dns-synthesize.h"
+#include "resolved-etc-hosts.h"
+#include "socket-netlink.h"
+#include "stat-util.h"
+#include "string-util.h"
+#include "strv.h"
+#include "time-util.h"
+
+/* Recheck /etc/hosts at most once every 2s */
+#define ETC_HOSTS_RECHECK_USEC (2*USEC_PER_SEC)
+
+static void etc_hosts_item_free(EtcHostsItem *item) {
+ strv_free(item->names);
+ free(item);
+}
+
+static void etc_hosts_item_by_name_free(EtcHostsItemByName *item) {
+ free(item->name);
+ free(item->addresses);
+ free(item);
+}
+
+void etc_hosts_free(EtcHosts *hosts) {
+ hosts->by_address = hashmap_free_with_destructor(hosts->by_address, etc_hosts_item_free);
+ hosts->by_name = hashmap_free_with_destructor(hosts->by_name, etc_hosts_item_by_name_free);
+ hosts->no_address = set_free_free(hosts->no_address);
+}
+
+void manager_etc_hosts_flush(Manager *m) {
+ etc_hosts_free(&m->etc_hosts);
+ m->etc_hosts_stat = (struct stat) {};
+}
+
+static int parse_line(EtcHosts *hosts, unsigned nr, const char *line) {
+ _cleanup_free_ char *address_str = NULL;
+ struct in_addr_data address = {};
+ bool found = false;
+ EtcHostsItem *item;
+ int r;
+
+ assert(hosts);
+ assert(line);
+
+ r = extract_first_word(&line, &address_str, NULL, EXTRACT_RELAX);
+ if (r < 0)
+ return log_error_errno(r, "/etc/hosts:%u: failed to extract address: %m", nr);
+ assert(r > 0); /* We already checked that the line is not empty, so it should contain *something* */
+
+ r = in_addr_ifindex_from_string_auto(address_str, &address.family, &address.address, NULL);
+ if (r < 0) {
+ log_warning_errno(r, "/etc/hosts:%u: address '%s' is invalid, ignoring: %m", nr, address_str);
+ return 0;
+ }
+
+ r = in_addr_data_is_null(&address);
+ if (r < 0) {
+ log_warning_errno(r, "/etc/hosts:%u: address '%s' is invalid, ignoring: %m", nr, address_str);
+ return 0;
+ }
+ if (r > 0)
+ /* This is an 0.0.0.0 or :: item, which we assume means that we shall map the specified hostname to
+ * nothing. */
+ item = NULL;
+ else {
+ /* If this is a normal address, then simply add entry mapping it to the specified names */
+
+ item = hashmap_get(hosts->by_address, &address);
+ if (!item) {
+ r = hashmap_ensure_allocated(&hosts->by_address, &in_addr_data_hash_ops);
+ if (r < 0)
+ return log_oom();
+
+ item = new(EtcHostsItem, 1);
+ if (!item)
+ return log_oom();
+
+ *item = (EtcHostsItem) {
+ .address = address,
+ };
+
+ r = hashmap_put(hosts->by_address, &item->address, item);
+ if (r < 0) {
+ free(item);
+ return log_oom();
+ }
+ }
+ }
+
+ for (;;) {
+ _cleanup_free_ char *name = NULL;
+ EtcHostsItemByName *bn;
+
+ r = extract_first_word(&line, &name, NULL, EXTRACT_RELAX);
+ if (r < 0)
+ return log_error_errno(r, "/etc/hosts:%u: couldn't extract hostname: %m", nr);
+ if (r == 0)
+ break;
+
+ found = true;
+
+ r = dns_name_is_valid_ldh(name);
+ if (r <= 0) {
+ if (r < 0)
+ log_warning_errno(r, "/etc/hosts:%u: Failed to check the validity of hostname \"%s\", ignoring: %m", nr, name);
+ else
+ log_warning("/etc/hosts:%u: hostname \"%s\" is not valid, ignoring.", nr, name);
+ continue;
+ }
+
+ if (!item) {
+ /* Optimize the case where we don't need to store any addresses, by storing
+ * only the name in a dedicated Set instead of the hashmap */
+
+ r = set_ensure_consume(&hosts->no_address, &dns_name_hash_ops, TAKE_PTR(name));
+ if (r < 0)
+ return r;
+
+ continue;
+ }
+
+ r = strv_extend_with_size(&item->names, &item->n_names, name);
+ if (r < 0)
+ return log_oom();
+
+ bn = hashmap_get(hosts->by_name, name);
+ if (!bn) {
+ r = hashmap_ensure_allocated(&hosts->by_name, &dns_name_hash_ops);
+ if (r < 0)
+ return log_oom();
+
+ bn = new0(EtcHostsItemByName, 1);
+ if (!bn)
+ return log_oom();
+
+ r = hashmap_put(hosts->by_name, name, bn);
+ if (r < 0) {
+ free(bn);
+ return log_oom();
+ }
+
+ bn->name = TAKE_PTR(name);
+ }
+
+ if (!GREEDY_REALLOC(bn->addresses, bn->n_addresses + 1))
+ return log_oom();
+
+ bn->addresses[bn->n_addresses++] = &item->address;
+ }
+
+ if (!found)
+ log_warning("/etc/hosts:%u: line is missing any hostnames", nr);
+
+ return 0;
+}
+
+static void strip_localhost(EtcHosts *hosts) {
+ static const struct in_addr_data local_in_addrs[] = {
+ {
+ .family = AF_INET,
+#if __BYTE_ORDER == __LITTLE_ENDIAN
+ /* We want constant expressions here, that's why we don't use htole32() here */
+ .address.in.s_addr = UINT32_C(0x0100007F),
+#else
+ .address.in.s_addr = UINT32_C(0x7F000001),
+#endif
+ },
+ {
+ .family = AF_INET6,
+ .address.in6 = IN6ADDR_LOOPBACK_INIT,
+ },
+ };
+
+ EtcHostsItem *item;
+
+ assert(hosts);
+
+ /* Removes the 'localhost' entry from what we loaded. But only if the mapping is exclusively between
+ * 127.0.0.1 and localhost (or aliases to that we recognize). If there's any other name assigned to
+ * it, we leave the entry in.
+ *
+ * This way our regular synthesizing can take over, but only if it would result in the exact same
+ * mappings. */
+
+ for (size_t j = 0; j < ELEMENTSOF(local_in_addrs); j++) {
+ bool all_localhost, in_order;
+
+ item = hashmap_get(hosts->by_address, local_in_addrs + j);
+ if (!item)
+ continue;
+
+ /* Check whether all hostnames the loopback address points to are localhost ones */
+ all_localhost = true;
+ STRV_FOREACH(i, item->names)
+ if (!is_localhost(*i)) {
+ all_localhost = false;
+ break;
+ }
+
+ if (!all_localhost) /* Not all names are localhost, hence keep the entries for this address. */
+ continue;
+
+ /* Now check if the names listed for this address actually all point back just to this
+ * address (or the other loopback address). If not, let's stay away from this too. */
+ in_order = true;
+ STRV_FOREACH(i, item->names) {
+ EtcHostsItemByName *n;
+ bool all_local_address;
+
+ n = hashmap_get(hosts->by_name, *i);
+ if (!n) /* No reverse entry? Then almost certainly the entry already got deleted from
+ * the previous iteration of this loop, i.e. via the other protocol */
+ break;
+
+ /* Now check if the addresses of this item are all localhost addresses */
+ all_local_address = true;
+ for (size_t m = 0; m < n->n_addresses; m++)
+ if (!in_addr_is_localhost(n->addresses[m]->family, &n->addresses[m]->address)) {
+ all_local_address = false;
+ break;
+ }
+
+ if (!all_local_address) {
+ in_order = false;
+ break;
+ }
+ }
+
+ if (!in_order)
+ continue;
+
+ STRV_FOREACH(i, item->names) {
+ EtcHostsItemByName *n;
+
+ n = hashmap_remove(hosts->by_name, *i);
+ if (n)
+ etc_hosts_item_by_name_free(n);
+ }
+
+ assert_se(hashmap_remove(hosts->by_address, local_in_addrs + j) == item);
+ etc_hosts_item_free(item);
+ }
+}
+
+int etc_hosts_parse(EtcHosts *hosts, FILE *f) {
+ _cleanup_(etc_hosts_free) EtcHosts t = {};
+ unsigned nr = 0;
+ int r;
+
+ for (;;) {
+ _cleanup_free_ char *line = NULL;
+ char *l;
+
+ r = read_line(f, LONG_LINE_MAX, &line);
+ if (r < 0)
+ return log_error_errno(r, "Failed to read /etc/hosts: %m");
+ if (r == 0)
+ break;
+
+ nr++;
+
+ l = strchr(line, '#');
+ if (l)
+ *l = '\0';
+
+ l = strstrip(line);
+ if (isempty(l))
+ continue;
+
+ r = parse_line(&t, nr, l);
+ if (r < 0)
+ return r;
+ }
+
+ strip_localhost(&t);
+
+ etc_hosts_free(hosts);
+ *hosts = t;
+ t = (EtcHosts) {}; /* prevent cleanup */
+ return 0;
+}
+
+static int manager_etc_hosts_read(Manager *m) {
+ _cleanup_fclose_ FILE *f = NULL;
+ struct stat st;
+ usec_t ts;
+ int r;
+
+ assert_se(sd_event_now(m->event, CLOCK_BOOTTIME, &ts) >= 0);
+
+ /* See if we checked /etc/hosts recently already */
+ if (m->etc_hosts_last != USEC_INFINITY && m->etc_hosts_last + ETC_HOSTS_RECHECK_USEC > ts)
+ return 0;
+
+ m->etc_hosts_last = ts;
+
+ if (m->etc_hosts_stat.st_mode != 0) {
+ if (stat("/etc/hosts", &st) < 0) {
+ if (errno != ENOENT)
+ return log_error_errno(errno, "Failed to stat /etc/hosts: %m");
+
+ manager_etc_hosts_flush(m);
+ return 0;
+ }
+
+ /* Did the mtime or ino/dev change? If not, there's no point in re-reading the file. */
+ if (stat_inode_unmodified(&m->etc_hosts_stat, &st))
+ return 0;
+ }
+
+ f = fopen("/etc/hosts", "re");
+ if (!f) {
+ if (errno != ENOENT)
+ return log_error_errno(errno, "Failed to open /etc/hosts: %m");
+
+ manager_etc_hosts_flush(m);
+ return 0;
+ }
+
+ /* Take the timestamp at the beginning of processing, so that any changes made later are read on the next
+ * invocation */
+ r = fstat(fileno(f), &st);
+ if (r < 0)
+ return log_error_errno(errno, "Failed to fstat() /etc/hosts: %m");
+
+ r = etc_hosts_parse(&m->etc_hosts, f);
+ if (r < 0)
+ return r;
+
+ m->etc_hosts_stat = st;
+ m->etc_hosts_last = ts;
+
+ return 1;
+}
+
+int manager_etc_hosts_lookup(Manager *m, DnsQuestion* q, DnsAnswer **answer) {
+ bool found_a = false, found_aaaa = false;
+ struct in_addr_data k = {};
+ EtcHostsItemByName *bn;
+ DnsResourceKey *t;
+ const char *name;
+ unsigned i;
+ int r;
+
+ assert(m);
+ assert(q);
+ assert(answer);
+
+ if (!m->read_etc_hosts)
+ return 0;
+
+ (void) manager_etc_hosts_read(m);
+
+ name = dns_question_first_name(q);
+ if (!name)
+ return 0;
+
+ r = dns_name_address(name, &k.family, &k.address);
+ if (r > 0) {
+ EtcHostsItem *item;
+ DnsResourceKey *found_ptr = NULL;
+
+ item = hashmap_get(m->etc_hosts.by_address, &k);
+ if (!item)
+ return 0;
+
+ /* We have an address in /etc/hosts that matches the queried name. Let's return successful. Actual data
+ * we'll only return if the request was for PTR. */
+
+ DNS_QUESTION_FOREACH(t, q) {
+ if (!IN_SET(t->type, DNS_TYPE_PTR, DNS_TYPE_ANY))
+ continue;
+ if (!IN_SET(t->class, DNS_CLASS_IN, DNS_CLASS_ANY))
+ continue;
+
+ r = dns_name_equal(dns_resource_key_name(t), name);
+ if (r < 0)
+ return r;
+ if (r > 0) {
+ found_ptr = t;
+ break;
+ }
+ }
+
+ if (found_ptr) {
+ r = dns_answer_reserve(answer, item->n_names);
+ if (r < 0)
+ return r;
+
+ STRV_FOREACH(n, item->names) {
+ _cleanup_(dns_resource_record_unrefp) DnsResourceRecord *rr = NULL;
+
+ rr = dns_resource_record_new(found_ptr);
+ if (!rr)
+ return -ENOMEM;
+
+ rr->ptr.name = strdup(*n);
+ if (!rr->ptr.name)
+ return -ENOMEM;
+
+ r = dns_answer_add(*answer, rr, 0, DNS_ANSWER_AUTHENTICATED, NULL);
+ if (r < 0)
+ return r;
+ }
+ }
+
+ return 1;
+ }
+
+ bn = hashmap_get(m->etc_hosts.by_name, name);
+ if (bn) {
+ r = dns_answer_reserve(answer, bn->n_addresses);
+ if (r < 0)
+ return r;
+ } else {
+ /* Check if name was listed with no address. If yes, continue to return an answer. */
+ if (!set_contains(m->etc_hosts.no_address, name))
+ return 0;
+ }
+
+ DNS_QUESTION_FOREACH(t, q) {
+ if (!IN_SET(t->type, DNS_TYPE_A, DNS_TYPE_AAAA, DNS_TYPE_ANY))
+ continue;
+ if (!IN_SET(t->class, DNS_CLASS_IN, DNS_CLASS_ANY))
+ continue;
+
+ r = dns_name_equal(dns_resource_key_name(t), name);
+ if (r < 0)
+ return r;
+ if (r == 0)
+ continue;
+
+ if (IN_SET(t->type, DNS_TYPE_A, DNS_TYPE_ANY))
+ found_a = true;
+ if (IN_SET(t->type, DNS_TYPE_AAAA, DNS_TYPE_ANY))
+ found_aaaa = true;
+
+ if (found_a && found_aaaa)
+ break;
+ }
+
+ for (i = 0; bn && i < bn->n_addresses; i++) {
+ _cleanup_(dns_resource_record_unrefp) DnsResourceRecord *rr = NULL;
+
+ if ((!found_a && bn->addresses[i]->family == AF_INET) ||
+ (!found_aaaa && bn->addresses[i]->family == AF_INET6))
+ continue;
+
+ r = dns_resource_record_new_address(&rr, bn->addresses[i]->family, &bn->addresses[i]->address, bn->name);
+ if (r < 0)
+ return r;
+
+ r = dns_answer_add(*answer, rr, 0, DNS_ANSWER_AUTHENTICATED, NULL);
+ if (r < 0)
+ return r;
+ }
+
+ return found_a || found_aaaa;
+}
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